The invention generally relates to stoppers, typically made of plastic, comprising a tubular skirt designed to surround the neck of a container to be stoppered, and to be fastened thereto in a removable manner by jamming with at least one inner snap of this skirt having an external projecting boss of the neck. These stoppers are generally called “snap-on” stoppers. They are also sometimes called clip-on stoppers.
This type of stopper is basically less difficult to detach from a container neck than are screw stoppers, the latter having to be drawn while rotating about themselves with respect to the neck in order to be able to open and close them. However, by nature, “snap-on” stoppers have a certain resistance to opening, which must be overcome in order to unsnap them, i.e., release them relative to the neck. To more easily apply a corresponding effort to draw the stopper in order to open it, it is known how to provide the external surface of the skirt with a boss to be grasped by a user with one finger. FR-A-2 908.746 provides such an example. However, even with the aid of such a tab, manipulating these stoppers in order to open them is difficult, especially for certain users who may have difficulty grabbing the skirt with sufficient firmness in order to unsnap it from the neck. Moreover, this difficulty may be more apparent during initial opening of stoppers incorporating means for evidencing this initial opening and designed to be broken by a user wishing to unsnap the skirt for the first time.
US 2013/0161327 proposes the use of an annular opening strip to make it easier to open a “snap-on” stopper. Part of this opening strip is permanently connected to the skirt of the stopper by a hinge allowing for toggling the opening strip between a position folded down against the skirt and an unfolded position in relation to the skirt. In the folded-down position, the opening strip is pressed horizontally against the upper end of the skirt, except in the last embodiment, in which the opening strip girds the skirt, i.e., a top part of the skirt, whose outside diameter is less than that of a lower part of the skirt, remains radially distant from the opening strip, whereas the aforesaid lower part is enclosed by the opening strip, while being connected to the lower end edge of the latter by the hinge. This solution makes it necessary to maintain the level of the lower end edge of the opening strip above that of the lower end edge of the skirt, whereby the offset between these two levels makes it possible to accommodate the hinge.
This means that anti-tampering safety is low, in the sense that it is easy to use a tampering tool to unsnap the skirt locally without damaging or moving the retaining strip in the folded-down position and the hinge.
The aim of the present invention is to propose a “snap-on” stopper, which, while being easy to manufacture and place on a container neck, is both easy to open, even in the case where the stopper incorporates tamper-evident means, and difficult to defeat.
Thus, the object of the invention is a stopper for a container neck, as defined in Claim 1.